0026734: Visualization, TKOpenGl - drop outdated UserDraw interfaces

0026734: Visualization, TKOpenGl - drop outdated UserDraw interfaces

Update ViewerTest and VoxelDemo to not use UserDraw callbacks.

OpenGl_View::blitBuffers() - set 0 GLSL program after blit
to avoid side effects on code that does not use shaders.

Drop interfaces Aspect_GraphicCallbackProc, Graphic3d_CUserDraw,
Graphic3d_Group::UserDraw(), OpenGl_GraphicDriver::UserDrawCallback().

V3d_View::SetWindow() - remove optional arguments initializing redraw callback.
OpenGl_View, declare following methods as virtual for inheritance:
redraw(), redrawImmediate(), render(), renderScene(), drawBackground(), renderStructs().

VocelClient_VisDrawer - do not include removed header